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path: root/drivers/gpio/gpiolib.c
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Diffstat (limited to 'drivers/gpio/gpiolib.c')
-rw-r--r--drivers/gpio/gpiolib.c255
1 files changed, 249 insertions, 6 deletions
diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 51a8d4103be5..662ed923d9eb 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -1,5 +1,6 @@
#include <linux/kernel.h>
#include <linux/module.h>
+#include <linux/interrupt.h>
#include <linux/irq.h>
#include <linux/spinlock.h>
#include <linux/device.h>
@@ -7,6 +8,7 @@
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#include <linux/gpio.h>
+#include <linux/idr.h>
/* Optional implementation infrastructure for GPIO interfaces.
@@ -49,6 +51,13 @@ struct gpio_desc {
#define FLAG_RESERVED 2
#define FLAG_EXPORT 3 /* protected by sysfs_lock */
#define FLAG_SYSFS 4 /* exported via /sys/class/gpio/control */
+#define FLAG_TRIG_FALL 5 /* trigger on falling edge */
+#define FLAG_TRIG_RISE 6 /* trigger on rising edge */
+
+#define PDESC_ID_SHIFT 16 /* add new flags before this one */
+
+#define GPIO_FLAGS_MASK ((1 << PDESC_ID_SHIFT) - 1)
+#define GPIO_TRIGGER_MASK (BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE))
#ifdef CONFIG_DEBUG_FS
const char *label;
@@ -56,6 +65,15 @@ struct gpio_desc {
};
static struct gpio_desc gpio_desc[ARCH_NR_GPIOS];
+#ifdef CONFIG_GPIO_SYSFS
+struct poll_desc {
+ struct work_struct work;
+ struct sysfs_dirent *value_sd;
+};
+
+static struct idr pdesc_idr;
+#endif
+
static inline void desc_set_label(struct gpio_desc *d, const char *label)
{
#ifdef CONFIG_DEBUG_FS
@@ -188,10 +206,10 @@ static DEFINE_MUTEX(sysfs_lock);
* /value
* * always readable, subject to hardware behavior
* * may be writable, as zero/nonzero
- *
- * REVISIT there will likely be an attribute for configuring async
- * notifications, e.g. to specify polling interval or IRQ trigger type
- * that would for example trigger a poll() on the "value".
+ * /edge
+ * * configures behavior of poll(2) on /value
+ * * available only if pin can generate IRQs on input
+ * * is read/write as "none", "falling", "rising", or "both"
*/
static ssize_t gpio_direction_show(struct device *dev,
@@ -288,6 +306,175 @@ static ssize_t gpio_value_store(struct device *dev,
static /*const*/ DEVICE_ATTR(value, 0644,
gpio_value_show, gpio_value_store);
+static irqreturn_t gpio_sysfs_irq(int irq, void *priv)
+{
+ struct work_struct *work = priv;
+
+ schedule_work(work);
+ return IRQ_HANDLED;
+}
+
+static void gpio_notify_sysfs(struct work_struct *work)
+{
+ struct poll_desc *pdesc;
+
+ pdesc = container_of(work, struct poll_desc, work);
+ sysfs_notify_dirent(pdesc->value_sd);
+}
+
+static int gpio_setup_irq(struct gpio_desc *desc, struct device *dev,
+ unsigned long gpio_flags)
+{
+ struct poll_desc *pdesc;
+ unsigned long irq_flags;
+ int ret, irq, id;
+
+ if ((desc->flags & GPIO_TRIGGER_MASK) == gpio_flags)
+ return 0;
+
+ irq = gpio_to_irq(desc - gpio_desc);
+ if (irq < 0)
+ return -EIO;
+
+ id = desc->flags >> PDESC_ID_SHIFT;
+ pdesc = idr_find(&pdesc_idr, id);
+ if (pdesc) {
+ free_irq(irq, &pdesc->work);
+ cancel_work_sync(&pdesc->work);
+ }
+
+ desc->flags &= ~GPIO_TRIGGER_MASK;
+
+ if (!gpio_flags) {
+ ret = 0;
+ goto free_sd;
+ }
+
+ irq_flags = IRQF_SHARED;
+ if (test_bit(FLAG_TRIG_FALL, &gpio_flags))
+ irq_flags |= IRQF_TRIGGER_FALLING;
+ if (test_bit(FLAG_TRIG_RISE, &gpio_flags))
+ irq_flags |= IRQF_TRIGGER_RISING;
+
+ if (!pdesc) {
+ pdesc = kmalloc(sizeof(*pdesc), GFP_KERNEL);
+ if (!pdesc) {
+ ret = -ENOMEM;
+ goto err_out;
+ }
+
+ do {
+ ret = -ENOMEM;
+ if (idr_pre_get(&pdesc_idr, GFP_KERNEL))
+ ret = idr_get_new_above(&pdesc_idr,
+ pdesc, 1, &id);
+ } while (ret == -EAGAIN);
+
+ if (ret)
+ goto free_mem;
+
+ desc->flags &= GPIO_FLAGS_MASK;
+ desc->flags |= (unsigned long)id << PDESC_ID_SHIFT;
+
+ if (desc->flags >> PDESC_ID_SHIFT != id) {
+ ret = -ERANGE;
+ goto free_id;
+ }
+
+ pdesc->value_sd = sysfs_get_dirent(dev->kobj.sd, "value");
+ if (!pdesc->value_sd) {
+ ret = -ENODEV;
+ goto free_id;
+ }
+ INIT_WORK(&pdesc->work, gpio_notify_sysfs);
+ }
+
+ ret = request_irq(irq, gpio_sysfs_irq, irq_flags,
+ "gpiolib", &pdesc->work);
+ if (ret)
+ goto free_sd;
+
+ desc->flags |= gpio_flags;
+ return 0;
+
+free_sd:
+ sysfs_put(pdesc->value_sd);
+free_id:
+ idr_remove(&pdesc_idr, id);
+ desc->flags &= GPIO_FLAGS_MASK;
+free_mem:
+ kfree(pdesc);
+err_out:
+ return ret;
+}
+
+static const struct {
+ const char *name;
+ unsigned long flags;
+} trigger_types[] = {
+ { "none", 0 },
+ { "falling", BIT(FLAG_TRIG_FALL) },
+ { "rising", BIT(FLAG_TRIG_RISE) },
+ { "both", BIT(FLAG_TRIG_FALL) | BIT(FLAG_TRIG_RISE) },
+};
+
+static ssize_t gpio_edge_show(struct device *dev,
+ struct device_attribute *attr, char *buf)
+{
+ const struct gpio_desc *desc = dev_get_drvdata(dev);
+ ssize_t status;
+
+ mutex_lock(&sysfs_lock);
+
+ if (!test_bit(FLAG_EXPORT, &desc->flags))
+ status = -EIO;
+ else {
+ int i;
+
+ status = 0;
+ for (i = 0; i < ARRAY_SIZE(trigger_types); i++)
+ if ((desc->flags & GPIO_TRIGGER_MASK)
+ == trigger_types[i].flags) {
+ status = sprintf(buf, "%s\n",
+ trigger_types[i].name);
+ break;
+ }
+ }
+
+ mutex_unlock(&sysfs_lock);
+ return status;
+}
+
+static ssize_t gpio_edge_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t size)
+{
+ struct gpio_desc *desc = dev_get_drvdata(dev);
+ ssize_t status;
+ int i;
+
+ for (i = 0; i < ARRAY_SIZE(trigger_types); i++)
+ if (sysfs_streq(trigger_types[i].name, buf))
+ goto found;
+ return -EINVAL;
+
+found:
+ mutex_lock(&sysfs_lock);
+
+ if (!test_bit(FLAG_EXPORT, &desc->flags))
+ status = -EIO;
+ else {
+ status = gpio_setup_irq(desc, dev, trigger_types[i].flags);
+ if (!status)
+ status = size;
+ }
+
+ mutex_unlock(&sysfs_lock);
+
+ return status;
+}
+
+static DEVICE_ATTR(edge, 0644, gpio_edge_show, gpio_edge_store);
+
static const struct attribute *gpio_attrs[] = {
&dev_attr_direction.attr,
&dev_attr_value.attr,
@@ -473,7 +660,7 @@ int gpio_export(unsigned gpio, bool direction_may_change)
struct device *dev;
dev = device_create(&gpio_class, desc->chip->dev, MKDEV(0, 0),
- desc, ioname ? ioname : "gpio%d", gpio);
+ desc, ioname ? ioname : "gpio%d", gpio);
if (dev) {
if (direction_may_change)
status = sysfs_create_group(&dev->kobj,
@@ -481,6 +668,14 @@ int gpio_export(unsigned gpio, bool direction_may_change)
else
status = device_create_file(dev,
&dev_attr_value);
+
+ if (!status && gpio_to_irq(gpio) >= 0
+ && (direction_may_change
+ || !test_bit(FLAG_IS_OUT,
+ &desc->flags)))
+ status = device_create_file(dev,
+ &dev_attr_edge);
+
if (status != 0)
device_unregister(dev);
} else
@@ -505,6 +700,51 @@ static int match_export(struct device *dev, void *data)
}
/**
+ * gpio_export_link - create a sysfs link to an exported GPIO node
+ * @dev: device under which to create symlink
+ * @name: name of the symlink
+ * @gpio: gpio to create symlink to, already exported
+ *
+ * Set up a symlink from /sys/.../dev/name to /sys/class/gpio/gpioN
+ * node. Caller is responsible for unlinking.
+ *
+ * Returns zero on success, else an error.
+ */
+int gpio_export_link(struct device *dev, const char *name, unsigned gpio)
+{
+ struct gpio_desc *desc;
+ int status = -EINVAL;
+
+ if (!gpio_is_valid(gpio))
+ goto done;
+
+ mutex_lock(&sysfs_lock);
+
+ desc = &gpio_desc[gpio];
+
+ if (test_bit(FLAG_EXPORT, &desc->flags)) {
+ struct device *tdev;
+
+ tdev = class_find_device(&gpio_class, NULL, desc, match_export);
+ if (tdev != NULL) {
+ status = sysfs_create_link(&dev->kobj, &tdev->kobj,
+ name);
+ } else {
+ status = -ENODEV;
+ }
+ }
+
+ mutex_unlock(&sysfs_lock);
+
+done:
+ if (status)
+ pr_debug("%s: gpio%d status %d\n", __func__, gpio, status);
+
+ return status;
+}
+EXPORT_SYMBOL_GPL(gpio_export_link);
+
+/**
* gpio_unexport - reverse effect of gpio_export()
* @gpio: gpio to make unavailable
*
@@ -527,6 +767,7 @@ void gpio_unexport(unsigned gpio)
dev = class_find_device(&gpio_class, NULL, desc, match_export);
if (dev) {
+ gpio_setup_irq(desc, dev, 0);
clear_bit(FLAG_EXPORT, &desc->flags);
put_device(dev);
device_unregister(dev);
@@ -611,6 +852,8 @@ static int __init gpiolib_sysfs_init(void)
unsigned long flags;
unsigned gpio;
+ idr_init(&pdesc_idr);
+
status = class_register(&gpio_class);
if (status < 0)
return status;
@@ -1244,7 +1487,7 @@ static int gpiolib_open(struct inode *inode, struct file *file)
return single_open(file, gpiolib_show, NULL);
}
-static struct file_operations gpiolib_operations = {
+static const struct file_operations gpiolib_operations = {
.open = gpiolib_open,
.read = seq_read,
.llseek = seq_lseek,
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.